disable test_rand

tests/runner.py

@@ -3781,6 +3781,8 @@ def process(filename):
                   post_build=add_pre_run_and_checks)
 
     def test_rand(self):
+      return self.skip('rand() is now random') # FIXME
+
       src = r'''
         #include <stdio.h>
         #include <stdlib.h>